Insulating rope with adsorbent material

ABSTRACT

An insulating rope includes: a non-conductive core; an extruded thermoplastic jacket disposed around the core; and a water adsorbent material disposed between the jacket and the core. A method of making an insulating rope is also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patentapplication Ser. No. 63/351,992, filed on Jun. 14, 2022.

TECHNICAL FIELD

The invention relates to insulating ropes having a low dielectricconstant so as to be electrically insulating, and in particular toinsulating ropes containing a water adsorbent material.

BACKGROUND

Insulating ropes (commonly referred to as “dielectric ropes”,“insulative ropes”, “dielectric cables”, “insulating cables”, or“insulative cables”) are used to protect workers on high-voltagetransmission lines, power stations, and other energized workenvironments from electric shocks and other dangers posed by thepresence of high voltages. They may be used in multiple applications,including live line working ropes, bare hand work, tag lines, handlines, pulling and stringing, evacuation and rescue, rope access,helicopter lift (helicopter longlines), safety netting and high strengthinsulating tool replacements. These insulating ropes must keep workerssafe even in the event that they come into contact with high voltageconductors or become energized through induction. In addition to havinga low dielectric constant, i.e., a high dielectric strength, themechanical properties of these ropes must be suited to theirapplication, for example tensile strength and flexibility. This imposescertain practical constraints on their manufacture.

If moisture is present inside the rope, the insulative properties of therope may be impaired. It is essential that the ropes maintain theirinsulating properties, to ensure the safety of the workers. To this end,the ropes should be tested regularly, and standards have beenestablished for this testing. A rope that fails a prescribed test mayneed to be discarded and replaced, due to the difficulty in removingmoisture from the interior of the rope. It is also possible that a ropemay lose its insulating properties in the time interval between tests,which poses some risk to workers.

One common method of isolating the ropes from moisture is by coating theropes with an overlay finish, such as a wax. However, this approach hasdrawbacks, such as making the ropes difficult to clean and maintain, andoccasionally trapping moisture, dirt, dust, or other contaminantsbetween the braid interstices of the rope, which can impair theinsulating properties of the rope.

Another common method of isolating the ropes from moisture is by coatingthem with an extruded thermoplastic jacket made from a hydrophobicmaterial such as polyurethane. Such a jacketed cable can have thedesired mechanical properties, and maintain its insulating propertieseven when wet. However, the ropes are often used in harsh conditions andmust be cleaned and maintained regularly, and are not always stored orused as recommended. Although these jacketed cables are highly reliable,it is still possible for moisture to occasionally penetrate the jacket,particularly if the rope is left submerged or exposed to high humidityfor long periods, or if the jacket is damaged during use. This canresult in the failure of the rope to maintain the required insulatingproperties, which poses a risk to workers and can reduce confidence inthe safety of the equipment.

Therefore, there is a desire in the art to further enhance the moistureresistance properties of insulating ropes.

SUMMARY

It is an object of the present invention to provide an insulating ropehaving improved resistance to water or humidity.

It is an object of the present invention to provide an insulating ropethat can maintain its insulating properties, even when exposed to highlevels of humidity during use or storage.

It is an object of the present invention to provide an insulating ropehaving an extruded thermoplastic jacket, that can maintain itsinsulating properties even when humidity penetrates inside the jacket.

According to a first aspect, an insulating rope includes: anon-conductive core; an extruded thermoplastic jacket disposed aroundthe core; and a water adsorbent material disposed between the jacket andthe core.

Optionally, in any of the previous aspects, the water adsorbent materialcomprises a zeolite or a metal-organic framework (MOF).

Optionally, in any of the previous aspects, the jacket comprisespolyurethane.

Optionally, in any of the previous aspects, the non-conductive corecomprises a twisted or braided rope.

Optionally, in any of the previous aspects, the braided rope comprisesat least one of ultra-high molecular weight polyethylene (UHMWPE),polyester, or aramid.

Optionally, in any of the previous aspects, the insulating rope includesat least one eye near at least one end thereof.

According to a second aspect, a method of making an insulating ropeincludes: applying a water adsorbent layer to a non-conductive rope; andapplying a thermoplastic jacket over the water adsorbent layer.

Optionally, in any of the previous aspects, the water adsorbent layercomprises a zeolite or a metal-organic framework (MOF).

Optionally, in any of the previous aspects, the non-conductive rope is atwisted or braided rope.

Optionally, in any of the previous aspects, the method includes urethanebonding the braided rope.

Optionally, in any of the previous aspects, applying the thermoplasticjacket comprises extruding the thermoplastic jacket over the wateradsorbent layer.

Optionally, in any of the previous aspects, the method includes coolingthe rope after extruding the thermoplastic jacket.

Optionally, in any of the previous aspects, the method includes sealingthe ends of the rope after applying the thermoplastic jacket.

Optionally, in any of the previous aspects, the method includes formingan eye near at least one end of the insulating rope.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, referencewill now be made to the accompanying drawings, showing by way ofillustration example embodiments thereof and in which:

FIG. 1 is a cut away view of an insulating rope according to anembodiment;

FIG. 2 is a perspective view of an insulating rope according to anembodiment;

FIG. 3 is a flow chart of a method of manufacturing an insulating ropeaccording to an embodiment; and

FIGS. 4A, 4B and 4C show high-voltage leakage current test results onexemplary insulating ropes according to an embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1 , an insulating rope 100 according to an embodimentwill be described. The insulating rope 100 includes a fiber core 102,which may be composed of any suitable dielectric material having asufficiently high tensile strength. Typical materials includeultra-high-molecular-weight polyethylene (UHMWPE), polyester, or aramidfibers (sometimes sold under the Kevlar™ brand). It should be understoodthat any suitable material or materials may be used for the core 102,provided that it has sufficient tensile strength and insulatingproperties for the intended use of the insulating rope 100. The fibersof the core 102 may be twisted into yarns and then cable-laid (twisted)or braided into a rope, to ensure a high tensile strength suitable forvarious different types of use.

Outside the core 102 is a water adsorbent layer 104. The water adsorbentlayer 104 contains a water adsorbent substance, for example a microsieve material such as a zeolite or a metal-organic framework (MOF). Itshould be understood that any suitable material or materials may be usedfor the water adsorbent layer 104, provided that it has sufficient wateradsorbent properties and does not impair the insulating properties ofthe insulating rope 100. For example, the water adsorbent layer 104 maycomprise a desiccant gel, an aluminosilicate, solid desiccants and/orother suitable hygroscopic materials. The water adsorbent layer 104 maycomprise a natural zeolite and/or a synthetic zeolite, for exampleanalcime, chabazite, clinoptilolite, erionite, mordenite, phillipsite,ferrierite, Linde-type zeolites, ZSM-5 and SSZ-32 zeolites.

Outside the water adsorbent layer 104 is a thermoplastic jacket 106. Thethermoplastic jacket 106 is hydrophobic, and its primary purpose is toprevent water or moisture from permeating the thermoplastic jacket 106and coming into contact with the core 102. It should be understood thatany suitable material or materials may be used for the thermoplasticjacket 106, provided that it is hydrophobic, sufficiently durable andflexible for the intended use of the insulating rope 100, and does notimpair the insulating properties of the insulating rope 100.

Referring to FIG. 2 , the insulating rope 100 may be spliced orotherwise fastened to form an eye 108 near one or both ends 110, whichcan be used for fastening the insulating rope 100 to other objects. Eacheye 108 may optionally include a thimble 112 to reinforce the eye,maintain its shape, and protect it from damage and wear. The thimble 112may be made of nylon or steel, or any other suitable material, dependingon the intended use of the insulating rope 100. In some embodiments, noeyes are formed at the ends of the rope 100, and the rope may beattached to other ropes or objects by knotting the rope. The ends 110are preferably sealed to prevent the entry of moisture or humidity intothe interior of the insulating rope 100.

Referring to FIG. 3 , a method 200 of manufacturing an insulating ropesuch as the insulating rope 100 will be described.

At step 202, multiple strands of an appropriately selected core fiberare twisted into yarns. The fiber may, for example, be UHMWPE,polyester, aramid, or any other suitable material.

At step 204, the yarns are cable-laid (twisted) or braided to form arope that may be used as the core 102.

At step 206, the rope is optionally urethane bonded to facilitatehandling and increase abrasion resistance.

At step 208, a water adsorbent layer is applied to the rope. This may bedone, for example, by applying a silicon-based spray coating or othersuitable adhesive to the rope, and then dipping the rope in a zeolitepowder or other suitable water adsorbent material. It is contemplatedthat other suitable methods may alternatively be used.

At step 210, a thermoplastic jacket is applied to the rope in one ormore layers. This may be done by extruding the thermoplastic materialover the rope. The thermoplastic material may, for example, be ahydrophobic material such as polyurethane. The thickness of the jacketmay be selected to provide sufficient durability and impermeability tohumidity and moisture, while still permitting sufficient flexibility ofthe finished rope.

At step 212, the ends of the rope are sealed, to form a hermeticallysealed system that prevents the entry of moisture.

At step 214, the completed rope is optionally cooled, to dissipate theheat generated during the extrusion process. The cooling may be done bypassing the rope through a tank or trough of water after extrusion.

At step 216, one or both ends of the rope are optionally spliced orotherwise fastened to form an eye. The eye may be formed around athimble, to reinforce the eye, maintain its shape, and protect it fromdamage and wear. Alternatively, this step may be omitted, in which caseno eyes are formed at the ends.

The insulating rope may optionally be cured.

Referring now to FIGS. 4A and 4B, dry and wet high voltage (HV) tests onexemplary insulating ropes according to the principles described hereinare presented. Dry tests comprised exposing insulating ropes comprisinga zeolite to 100 kV, 75 mA AC over 12″ with an ASTM disc for a period of5 minutes. Wet tests comprised placing insulating ropes comprising azeolite in a climatic chamber at 99% humidity of 100-ohm water for 16hours prior to testing, followed by exposure to 100 kV, 75 mA AC on 12″with an ASTM disc for a period of 5 minutes. It will be understood thatmV values may be converted to uA for the purpose of this disclosure bymultiplying the mV value by a factor of 10.

The insulating ropes according to the present invention exceeded currentacceptance standards. In particular, the insulating ropes meet andexceed current acceptance standards when exposed to 100 kV AC on 12inches. For example, a leakage current test comprising exposure to 100kV on 12 inches is approximately twice as severe as a currently acceptedASTM insulation test.

As shown in FIG. 4A, a dry leakage current test as described above on anabout ½″ insulating rope resulted in a maximum logged leakage current of1.92 uA, compared with a present ASTM acceptance threshold of 100 uA. Asshown in FIG. 4B, a wet leakage current test as described above on anabout ½″ insulating rope resulted in a maximum logged leakage current of2.47 uA, compared with a present ASTM acceptance threshold of 250 uA.

Referring now to FIG. 4C, a wet conditioning leakage current test on aninsulating rope comprising a zeolite according to the present inventionis presented. The wet high-voltage test comprised soaking insulatingropes according to the present invention in a basin of 100-ohmconductive water, immediately followed by leakage current testing at 100kV over 15 inches with an ASTM disc for a period of 5 minutes. Such atest may simulate a hypothetical worst case scenario where an insulatingrope is exposed to extremely wet conditions, for example extremelyintense rainfall. For example, the rope may be exposed to a flood or tointense rainfall while in unprotected storage, or be exposed to intenserainfall while in use by maintenance personnel, for example during anintense storm. The exemplary test shown in FIG. 4C comprised soaking aninsulating rope for 1 h as described above. As shown in FIG. 4C, themaximum logged leakage current was 2 uA, compared to a current wet ASTMacceptance threshold of 200 uA.

It will be understood that the broad principles and acceptancethresholds of ASTM standards may be applicable and/or substantiallysimilar to principles and acceptance thresholds of other standards, e.g.IEC standards, and that the insulating ropes according to the presentinvention exceed IEC and other recognized acceptance criteria as well.

Insulating ropes according to the present invention therefore providesubstantial security to personnel and equipment exposed to electricalcurrents, or working in conditions wherein support equipment, such asropes, may be in contact with an energized source while making contactwith the ground. For example, maintaining energy in a portion of anelectrical grid or in an electrical line during maintenance or repairwork may improve response, maintenance and repair times withoutcompromising user and/or worker safety.

An insulating rope as described herein has a low dielectric constant andtherefore a high dielectric strength, and is suitable for use inelectrified environments.

An insulating rope as described herein may have one or more advantagessuch as improved resistance to the penetration of humidity and moisture,improved reliability of the insulative properties of the rope, andincreased service life of the rope.

An insulating rope as described herein may provide improved usabilityand performance. For example, a user's ability to twist, knot, flex andotherwise deform the insulating rope during use may be improved withoutsacrificing user safety.

The insulating ropes according to the present invention met and exceededASTM insulation standards rapidly following production according to themethods disclosed herein. The production time of insulating ropes maycomprise several phases, including some or all of production planning,raw materials reception, material incorporation, extrusion, curing,batch testing, finishing and shipping.

Although some steps may be rate-limiting or difficult to shorten, thepresent invention provides a high-performance product that meets currentand future applicable standards and reduces the duration of themanufacturing process. Accordingly, manufacturers may respond rapidly tocustomer demand while reducing resource use

The embodiments described above are intended to be examples only. Thescope of the invention is therefore intended to be limited solely by theappended claims.

1. An insulating rope, comprising: a non-conductive core; an extrudedthermoplastic jacket disposed around the core; and a water adsorbentmaterial disposed between the jacket and the core.
 2. The insulatingrope of claim 1, wherein the water adsorbent material comprises azeolite or a metal-organic framework (MOF).
 3. The insulating rope ofclaim 1, wherein the jacket comprises polyurethane.
 4. The insulatingrope of claim 1, wherein the non-conductive core comprises a twisted orbraided rope.
 5. The insulating rope of claim 4, wherein the braidedrope comprises at least one of ultra-high molecular weight polyethylene(UHMWPE), polyester, or aramid.
 6. The insulating rope of claim 1,further comprising at least one eye near at least one end thereof. 7.The insulating rope of claim 1, wherein the insulating rope passes ASTMhigh voltage leakage current tests at 100 kV across 12 inches.
 8. Amethod of making an insulating rope, comprising: applying a wateradsorbent layer to a non-conductive rope; and applying a thermoplasticjacket over the water adsorbent layer.
 9. The method of claim 8, whereinthe water adsorbent layer comprises a zeolite or a metal-organicframework (MOF).
 10. The method of claim 8, wherein the non-conductiverope is a twisted or braided rope.
 11. The method of claim 10, furthercomprising urethane bonding the braided rope.
 12. The method of claim 8,wherein applying the thermoplastic jacket comprises extruding thethermoplastic jacket over the water adsorbent layer.
 13. The method ofclaim 12, further comprising cooling the rope after extruding thethermoplastic jacket.
 14. The method of claim 8, further comprisingsealing the ends of the rope after applying the thermoplastic jacket.15. The method of claim 8, further comprising forming an eye near atleast one end of the insulating rope.
 16. The method of claim 8, furthercomprising curing the insulating rope.